Safety Characteristics - Siemens SIPART PS2 Operating Instructions Manual

Functional safety

8.5 Safety characteristics

Protection against configuration changes
You should attach the housing cover so that the device is protected against unwanted and
unauthorized changes/operation.
Checking the safety function
Prerequisite for checking the safety function
● Positioner is in operation.
● The actuator belonging to the positioner is not in the safety position.
Procedure
● On the positioner, switch the signal source to 0 mA or the power supply source to 0 V.
● Reduce the inlet pressure (PZ) to a third of the maximum supply pressure.
● Always carry out the validation of the safety function with positioner and valve under
operating conditions.
Result
The actuator brings the valve to the specified safety position.
See also
Safety function (Page 131)
8.5 Safety characteristics
The safety characteristics necessary for use of the system are listed in the SIL declaration of
conformity. These values apply under the following conditions:
● The positioner is only used in applications with low demand rate for the "Low demand mode".
● The positioner is blocked against unwanted and unauthorized changes/operation.
● The signal source with 0 mA or the power supply source with 0 V for the SIPART PS2
positioner is generated by a safe system that fulfills SIL 2 for single-channel operation.
● The connected single-acting type actuator returns the valve to the safe end position by
spring force in the following scenarios:
– With a chamber pressure (Y1 connection) up to a third of the maximum available supply
● The air outlet does not contain any additional cross-sectional contractions leading to an
increased dynamic pressure. In particular, a silencer is only allowed if icing or other
contamination is ruled out.
● The restrictor in the Y1 circuit may not be completely closed during operation.
● The auxiliary pneumatic power is free of oil, water and dirt in line with:
DIN/ISO 8573-1, maximum class 2
● The average temperature viewed over a long period is 40 °C.
134
air pressure (PZ connection)
SIPART PS2 with and without HART
Operating Instructions, 05/2017, A5E00074631-AC